Expected lifetime of Petromax jets?

Discussion in 'Pressure Lamp Discussion Forum' started by Adrian, Oct 15, 2020.

  1. Adrian Romania

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    Just had a clone jet get badly enlarged after 4-5 uses (probably 10 hours or so in total). It may have had something with wrapping some aluminum foil around the pricker rod (maybe it was too tight in the "strangled" part of the upper generator and forced the needle against the jet, but still it's an incredibly short usefulness of a brand new jet.
    The needle didn't had any fishhook end (checked with a 10x magnifying glass before installing it).

    So now the question is: are original Petromax jets much more durable? How long can these be expected to last in normal use?
     
  2. george

    george United States Subscriber

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    A lot longer than this. Depends on how much you use the lantern. A good German Petromax will last a long time. I've had some that lasted years.
    The clones, I don't know but they should last a lot longer than yours.
     
  3. Adrian Romania

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    George, I believe that the nozzles/jets are usually enlarged by the steel needle going back and forth trough them. So probably the number of start/stop cycles is what kills the jets.
     
  4. george

    george United States Subscriber

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    You may be right but I would think even the clones would last longer then this.
    It's like buying a well established name brand car, great reviews, etc. So you buy it based on all the good reviews only to have it wind up the car from hell! Brake down after brake down!
     
  5. WimVe

    WimVe Subscriber

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    What IS an original Petromax part ?

    One from berlin,
    from Altena?,
    from Casa Hipolito?,
    from China ?
     
  6. Adrian Romania

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    Let's just narrow it down to "something not from China" :mrgreen:

    How many times one should expect to be able to pass the needle trough the jet (OK, that sounds weird :lol: ) before orange flames start appearing around the mantle?
     
  7. Fireexit1

    Fireexit1 United Kingdom Subscriber

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    I don't know - but I have several optimus and petromax/hiploito lamps of various ages, and although I have changed jets it is because they have come with the service kit and not because they needed changing. I am not sure where the new petromax jets in the latest petromax service kits come from but I have never had any problems. I think either you have been unlucky with the current jet or the problem is elsewhere.
     
  8. MYN

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    From my experience with both the Petromax and clones' jets, there aren't any appreciable lifespan differences.
    @Adrian ,
    The early failure as what you've described is very unlikely, even with the 'cheapest' of jets made from the softest brass anyone would use. The problem lies elsewhere.
    You could enlarge the orifice if the needle pricker is forcibly off-centre. Example, aluminium foil too tight around a pricker rod that was bent or already off-center when you move it upwards towards the jet. Or the hole at the constricted part of the generator is not aligned to the jet orifice.(possibly by a manufacturing defect on the generator).
    In general, a decent jet and pricker takes a long time to fail from mechanical wear by the needle. The real wear is from high velocity fuel flow at operating temperatures. Example, the seat of a partially opened valve wears much faster than a fully opened one. Check that the jet orifice is not partially blocked by the needle. If the height of the needle was not adjusted correctly, it could accentuate the problem.
     
  9. Adrian Romania

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    Thanks for the advice. I was thinking at the aluminum foil as well.

    Will test with a new jet and see how it goes. As a precaution I won't install any needle for the time being, if everything goes well I will remove the aluminum foil .
     
  10. JonD

    JonD Subscriber

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    Isn't this all down to tolerances in the machining? If the back drill process goes too deep it leaves the dome very thin.

    Easy to make the jet orifice but it will have little or no wear resistance to the needle. Can you measure it?
     
  11. Adrian Romania

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    Sadly no, I don't have anything suitable for holes that small.
     
  12. george

    george United States Subscriber

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    Maybe this is a dumb question, but have you checked the vaporizer? Could it be full of carbon?
     
  13. JonD

    JonD Subscriber

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    It's not an easy measurement to make.. here is my idea about it.
    It would need at least vernier calipers or even better some sort of micrometer.

    measure_dome.jpg
     
  14. Adrian Romania

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    I have vernier calipers but old style so anything below 1mm is just a guess. Plus there's no way to measure the dimension of the back drilling with them, the tails is too big to fit up to the tip of the drilled cone.
     
  15. Dieselross Germany

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    Moin,
    I've already experienced the problem with the bent needles myself several times when I received lamps for repair.
    There were always two clear reasons for defects in the nozzle and needle on Petromax lamps.
    1. Incorrect setting of the needle height and combined with incorrect operation of the lamp.
    (Burning and burning out because the needle was misused to regulate the brightness, with Petromax it is only fully open or completely closed.
    So light or off.)
    Or problems with the production quality of nozzles and needles from replica production.
    Needles that are badly pressed or badly centered, and badly deburred nozzles.

    Usually it helps to deburr the nozzle a little wider and rounder at the point where the needle is inserted, so that the needle can find its way into the center of the nozzle more easily.
    With Petromax lamps, the whole "needling" and cleaning the nozzle is not necessary as often as many users do. t
    The nozzle and the needle are very rarely worn; in an estimated 80% of cases, incorrect use and incorrect assembly lead to failures and defects.
    On the subject of aluminum foil, it must be said that with Petromax lamps there is the option of inserting a thin brass mesh into the carburetor.
    This network is used to heat the fuel more intensely through more surface in the carburetor in order to eliminate the slight pulsation in the brightness of some lamps and alternative fuels.
    The sense and use of aluminum foil is so far completely unknown to me.

    On the subject of spare parts, I can still say that the parts and seals from production before around 1990, i.e. old NOS stocks, already have significantly better manufacturing quality than the material that is produced today.
    The lead seals were much thicker and the needles and nozzles were cleaner manufactured.
    A clear sign that the production costs for spare parts that the military used and bought could be significantly higher than is possible today for private use.
     
  16. Adrian Romania

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    The foil is installed on the rod in the area between the lower and upper parts of the Preston loop. The idea was to force more fuel trough the loop but decreasing the tolerance between the rod and the constricted area of the vertical pipe.
     
  17. WimVe

    WimVe Subscriber

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    I have never heard of foil on the named location. The pricker/needle rod has at that said point a wider diameter to force fuel through the coil.
    I also don't see why this will influence the lifetime of the needle/jet.
    If the needle isn't set low enough, fuel will leave the jet different and maybe not in a straight line.
     
  18. Dieselross Germany

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    @Adrian
    Why did you try to change something with the foil?
    Besides the defects in the needles and nozzle, are there any other functional problems, or why did you try this modification?
    As described by Wim and others, I would eliminate the problem with the needle and nozzle with the correct setting.
     
  19. bp4willi

    bp4willi Germany Subscriber

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    @Adrian
    I observed the need for such alu foil in that position
    in a butterfly generator.

    The rod was simply not matching the bore hole in the narrow passage between the ends of the preston loop.

    Rod was too thin. All petro was passing by the loop on the straight path.
    So adding the alu foil helped.
     
  20. WimVe

    WimVe Subscriber

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    In such a case: buy a new rod.

    In the lifetime of a lantern owners can do strange things whith parts and modifications, like boring out the restriction to get more light.
    Or putting in the wrong size or combination of needle/jet.
     
  21. MYN

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    A perfect rather snug fit of the pricker rod at the constricted section is not absolutely necessary for a Preston loop vaporizer. There isn't much improvement in terms of actual performance.
    I've made my own pricker rod from a brass rod that slided through the constriction with as little clearance as practical(without seizing up in operation). Just to ensure that most of the fuel would take the looped path instead of getting straight through.
    But nope. That doesn't make it perform appreciably better than the regular rod.
    In actual operation, whatever fuel in the looped section would just expand in the heated vaporizer and disrupt the fuel flow at the constricted path. In effect, everything evens out and fuel would just vaporize as usual as it leaves the jet orifice. Even if there is no pricker rod obstructing the flow in the constricted section.
    The only difference is during start-ups immediately after spirit preheating. If the clearance between the rod and the inner wall of the constricted section is too great, you might get an initial yellow-flame flare up as you lower the needle during light ups. But as soon as the mantle lights up strongly, the entire upper vaporizer would be sufficiently heated up to negate any effects of the straight path. Some equilibrium would be attained.
     

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